Anode for electron discharge device



Oct. 28, 1958 w. GlLLlES ETAL ANODE FOR ELECTRON DISCHARGE DEVICE Filed April 1, 1955 Fig.4

INVENTQRS Wallace Gillies and Clifford E Horner.

WITNESSES'.

ATTORNEY ited States Patent ANODE FOR ELECTRON DISCHARGE DEVICE Wallace Gillies, Elmira, and Clifford E. Hornet, Watkins Glen, N. Y., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application April 1, 1955, Serial No. 498,502v

6 Claims; (Cl. 313-352) This invention relates to electron discharge devices and, more particularly, to the construction of anode elec-' trodes for electron discharge devices.

In prior art electron discharge devices, particularly thyratro-ns operating with appreciable average anode currents, anodes were subject to overheating due to short duration overload currents which caused rapid excessive increases in temperature. This overheating caused (l) distortion of the anode which frequently led to tube failure because of a short between the anode and an adjacent electrode; (2) mechanical failure of the spot welds used to attach the anode to the cathode support mem- "ber; and (3) undesirable vaporization of the anode material. Anodes were made of relatively thin (.020 inch) material because of the ease of fabrication and the lightness of weight.

It is an object of this invention to provide an improved anode in an electron discharge device with improved heat conduction.

It is another object of this invention to provide an improved anode in an electron discharge device with reduced structural distortion.

It isa further object to provide an improved method of using copper brazes in electron discharge devices.

It is a different object to provide an improved method of using silver brazes in electron discharge devices.

It is an additional object to provide an improved method of joining a first member to a second member in an electron discharge device.

These and other objects of the invention will be apparent from the following description, taken in accordance with the accompanying drawings which form a part of this application, and in which:

Figure 1 is a schematic view of a typical prior art electron discharge device, namely a thyratron gas triode;

Fig. 2 is a cross-sectional view of a typical prior art anode assembly for such an electron discharge device as shown in Fig. 1;

Fig. 3 is a cross-sectional view of an anode assembly showing an embodiment of my invention; and

Fig. 4 is a portion of Fig. 3 showing a metallic coating -over the brazed material.

In Fig. 1 there is shown an electron discharge device including an anode 11, a cathode 15, and a grid electrode 13 between the anode 11 and the cathode 15. The cathode is heated by a heater member 17. An anode cap member 19 provides a terminal for the anode 11. A suitable glass or metal envelope 21 encloses the electrode structure of the electron discharge device. In this case, the envelope 21 is filled with a suitable gas 23. The electron discharge device is supported by a base member 25.

In Fig. 2, there is shown an anode assembly 27 including a cup-shaped member 29 to which is attached an anode support member 31 and a lead member 33.

in Fig. 3, there is shown an anode assembly 35 embodying my invention and including a cup-shaped mem- 2,858,471 Patented Oct. 28, 1958 her 37 to which has been attached a disk member 39. Attached to the disk member 39 are an anode support member 41 and a lead member 43. Copper brazing material 45 is used to attach the members to each other.

In Fig. 4 there is shown an enlargement of a portion of Fig. 3 showing the cup-shaped member 37, the disk member 39, the copper brazing material 45 and a metal coating 47 which is positioned over at least the copper brazing material 45.

In accordance with my invention, a disk member 39 is brazed to an anode in an electron discharge device to provide improved heat conduction and to improve structural distortion in the anode without the addition of excessive additional weight. The brazing material 45 should exhibit a high heat conductivity. Materials such as copper or silver possess the necessary high heat conductivity but have had limited previous use in electron discharge devices because of their high vapor pressure at high temperatures. My invention allows the use of copper or silver brazing materials because the brazing material 45 is coated with a protective material 47 which has a lower vapor pressure than the brazing material 45 throughout the range of temperatures encountered during the manufacture and operation of the electron discharge device. In this way, the vaporization of the brazing material is reduced or eliminated.

Brazing is preferred to spot welding as a method of joining the disk member 39 to the cup member 37 because brazing provides a better flow of heat from the cup member 37 to the disk member 39 due to the better contact provided by the brazing.

In a suitable brazing operation, the members may be spot welded together or placed in positioning fixtures before being brazed. A ring of .050 inch copper wire is placed around the joint between the cup member 37 and disk member 39 and a ring of .025 inch copper wire 'is placed around the joint between the disk member 39 chromium and rhodium. Electroplating is a suitable method of coating the anode assembly with metal.

If the copper or silver braze is not coated with another metal, the copper or silver and their surface compounds tend to vaporize during heat treatment and operation. This vaporized copper or silver would be deposited on the envelope and the other electrodes of the electron discharge device causing contamination of the cathode which results in undesirably low cathode emission. Other undesirable defects of the copper or silver deposits are a lowering of the work function of the grid surfaces which results in undesirable high grid emission and coating of insulating materials in the electron discharge devices which results in undesirably high leakage currents. This vaporization and deposition of copper, silver and their compounds has previously restricted the use of copper, silver, copper alloys and silver alloys in electron discharge devices to applications where the temperature does not exceed approximately 600 C. during the manufacture and operation of the tube.

While the present invention has been shown in one form only, it will be obvious to those skilled in the art that it is not so limited but is susceptible of various changes and modifications without departing from the spirit thereof. For example, brazing materials other than copper, silver and copper or silver alloys may be used if they exhibit the necessary high heat conductivity.

Also members other than those specified in the disclosed embodiment in electron discharge devices may be joined by the brazing method described above.

We claim as our invention:

1. In an electron discharge device within an at least partially evacuated envelope, the combination of a cathode, at least one control grid and an anode, said anode including a cup member and a disk member, a braze between said cup member and said disk member, a layer of protective material coating said braze, said protective material being operable to reduce the vaporization of the surface layer of said braze during the manufacture and operation of the device.

2. In an electron discharge device within an at least partially evacuated envelope, the combination of a cathode, at least one control grid and an anode, said anode including a cup member and a disk member, a braze between said cup member and said disk member, a layer of protective material coating said braze, said protective material being operable to reduce the vaporization of the surface layer of said braze during manufacture and operation of the device, said protective material having a vapor pressure lower than the vapor pressure of the material of said braze throughout the range of temperatures encountered during the manufacture and operation of the electron discharge device.

3. In an electron discharge device within an at least partially evacuated envelope, the combination of a cathode, at least one control grid and an anode, said anode including a cup member, a disk member, and a support member, a first braze between said cup member and said disk member, a second braze between said disk member and said support member, and a layer of protective material coating said first braze and said second braze.

4. In an electron discharge device within an at least partially evacuated envelope, a combination of a cathode, at least One control grid and an anode, said anode including a cup member and a disk member, a braze between said cup member and said disk member, a layer of protective material coating said braze, said protective material having a lower Work function than the material of said braze.

5. In an electron discharge device within an at least partially evacuated envelope, the combination of a cathode and an anode, said anode including a cup member and a disk member, a braze between said cup member and said disk member, a layer of protective material coating said braze, said protective material being operable to reduce the vaporization of the surface layer of said braze during manufacture and operation of the device, the material of said braze being selected from the group consisting of copper, silver, copper alloys and silver alloys.

6. In an electron discharge device within an at least partially evacuated envelope, the combination of a cathode and an anode, said anode including a cup member and a disk member, a braze between said cup member and said disk member, a layer of protective material coating said braze, said protective material being operable to reduce the vaporization of the surface layer of said braze during manufacture and operation of the device, the material of said braze being selected from the group consisting of copper, silver, copper alloys and silver alloys, said protective material being selected from the group consisting of nickel, chromium and rhodium.

References Cited in the file of this patent UNITED STATES PATENTS Marshall May 3, 1955 

6. IN AN ELECTRON DISCHARGE DEVICE WITHIN AN AT LEAST PARTIALLY EVACUATED ENVELOPE, THE COMBINATION OF A CATHODE AND AN ANODE, SAID ANODE INCLUDING A CUP REMBER AND A DISK MEMBER, A BRAZE BETWEEN SAID CUP MEMBER AND SAID DISK MEMBER, A LAYER OF PROTECTIVE MATERIAL COATING SAID BRAZE, SAID PROTECTIVE MATERIAL BEING OPERABLE TO REDUCE THE VAPORIZATION OF THE SURFACE LAYER OF SAID BRAZE DURING MANUFACTURE AND OPERATION OF THE DEVICE, THE MATERIAL OF SAID BRAZE BEING SELECTED FROM THE GROUP CONSISTING OF COPPER, SILVER, COPPER ALLOYS AND SILVER ALLOYS, SAID PROTECTIVE MATERIAL BEING SELECTED FROM THE GROUP CONSISTING OF NICKEL, CHROMIUM AND RHODIUM. 